LITTLE ROCK (AP) — Arkansas’ just-approved execution law is as badly flawed as the version it replaced, according to a lawsuit filed Friday that argues the new law is unconstitutional and puts inmates at risk for an agonizing death.

The lawsuit was filed in Pulaski County Circuit Court on behalf of six death row inmates who argue that the law approved by legislators last month still violates existing law and is unconstitutional. The Arkansas Supreme Court last year tossed out the state’s previous execution law, saying the Legislature had ceded too much control to Correction Department administrators in carrying out executions.

Arkansas hasn’t executed an inmate since 2005 due to court challenges, and inmates’ attorney Jeff Rosenzweig said he expects this legal effort to kick around the courts for quite a while.

“I think these are meritorious claims that I think will take the courts a while to sort out. We’re dealing with a brand new statute, new procedures and a lot of complicated evidentiary issues,” Rosenzweig said.

The suit argues that the new procedures from the Legislature call for the use of an anti-anxiety drug and phenobarbital, a slow-acting barbiturate, in “a completely untried combination and quantity of drugs that will take hours to be injected and to reach their peak effect, that will produce agonizing and degrading effects during the procedure, and that will severely and permanently injure — but may not kill — the prisoners.”

Rosenzweig attacked the new measure on several points, one of which that the new law is in conflict with a 1983 law and “the well-settled state law principle that a sentence must be in accordance with the statutes in effect on the date of the crime.”

He repeats a concern that was raised about the previous law — that specifics are left to prison officials when it comes to deciding which barbiturate to use in executions. Rosenzweig also alleges problems with how the executioners are chosen by the department.

The Legislature consulted with Attorney General Dustin McDaniel’s office while the new law was being developed. Rosenzweig said he expected the new law to leave openings for a challenge.

“The attorney general was the one who pushed the law in 2009, which got set aside. I’m not completely surprised,” Rosenzweig said.

The Arkansas Attorney General’s Office is responsible for the state’s response, and a spokesman for the office said Friday that lawyers are reviewing the suit but had no further comment.

The Associated Press learned last week that the state had obtained doses of lorazepam, an anti-anxiety drug, and phenobarbital, a slow-acting barbiturate used to treat seizures, to use for executions. Prison spokeswoman Shea Wilson said phenobarbital was on a list of FDA-approved barbiturates in court papers filed by lawyers for the inmates in a previous case.

In a letter obtained by the AP this month, federal public defender Jenniffer Horan told Democratic Gov. Mike Beebe that phenobarbital takes effect more slowly than other drugs used to execute prisoners and that it carries a “substantial risk of a lingering and inhumane death.”

The Death Penalty Information Center said no state has ever used phenobarbital in an execution.